To my car to ford today complaining of poor economy and it been down on power after a few hours they found a paramenter wrong relating to my alloys as the standard car had 16" and I've upgraded to 17" I'm not suprised it's wrong so they have rectified that but couldn't find anything else and handed me a bill for £48 as its not covered under warranty not the power has improved and the mpg has gone from 42-52 which ain't brilliant for a deisel but I will take it for now. Has anyone else had this or actually believe fords story not sure if I do

Can you explain what the garage claimed to have found? If the wheels are Ford options they should be the correct outer diameter with the approriate tyre. I don't understand what they have charged you for.

Silly question but... can anyone do this? Be interested to see if they changed mine when I got it :s

No, only people with a Ford VCM (bit of kit that hooks up to a laptop)

Sam

Can you explain what the garage claimed to have found? If the wheels are Ford options they should be the correct outer diameter with the approriate tyre. I don't understand what they have charged you for.

There are settings for wheel/tyre diameter and size in the configuration parameters for the car (195/50/15, 195/45/16, 205/40/17) Whether this makes the engine compensate for heavier wheels or just adjusts the speedo I do not know.

No, only people with a Ford VCM (bit of kit that hooks up to a laptop)

There are settings for wheel/tyre diameter and size in the configuration parameters for the car (195/50/15, 195/45/16, 205/40/17) Whether this makes the engine compensate for heavier wheels or just adjusts the speedo I do not know.

Well all they claim to have changed is the setting you mentioned claiming that was the cause of all my problems and my mpg has risen by 10 mpg up to now the car is more responsive and the engine is silky smooth again so it obviously makes a big difference

Can you explain what the garage claimed to have found? If the wheels are Ford options they should be the correct outer diameter with the approriate tyre. I don't understand what they have charged you for.

My alloys are not ford options they are 17" fox fx004s it had the standard for 16" alloys when i bought it.anyway they claim to have the changed the parameter that tells the car what size wheels/ tyres are fitted to it from 16"-17" an it's made more I a difference than you'd think

Hmmm.. dubious claims. Heavier wheels won't make that kind of difference and you cannot change the gearing with electronics. If you have 17" rims with 40 section tyres these will give the same diameter as 16" rims with 45 section tyres.

Hmmm.. dubious claims. Heavier wheels won't make that kind of difference and you cannot change the gearing with electronics. If you have 17" rims with 40 section tyres these will give the same diameter as 16" rims with 45 section tyres.

Still if your happy then £48 aint bad.

Well I'm a bit dubious about what they did but it seems to have helped with my problems bu not quite solved them

Hmmm.. dubious claims. Heavier wheels won't make that kind of difference and you cannot change the gearing with electronics. If you have 17" rims with 40 section tyres these will give the same diameter as 16" rims with 45 section tyres.

You cannot change the gearing but I think you can change the odometer/speedo and trip computer reading to match the tyre diameter. You certainly could on my Saab 900 back in 1995! If Nathan says there is a setting for the tyre/wheel size on the Fiesta then I suspect that is exactly what it does. You can see the different overall wheel diameters using a calculator such as this one: http://www.etyres.co...-calculator.htm

My simple brain can't understand how a 17 inch wheel is different to a 16 inch wheel in any way (other than size and maybe a tiny, tiny bit of resistance for a 205 tyre over a 195) that can affect mpg so much and that could be changed by telling the ECU that you have different wheels. Would be interesting to know what they actually did...

I'm not sure that anything could change the actual mpg, but the change in tyre diameter and circumference will affect the INDICATED mpg on the trip computer. The mpg is influenced by the difference in distance recorded by one revolution of the wheel. This also affects the odometer and speedometer readings which is probably why the parameter is there to be changed.

My simple brain can't understand how a 17 inch wheel is different to a 16 inch wheel in any way (other than size and maybe a tiny, tiny bit of resistance for a 205 tyre over a 195) that can affect mpg so much and that could be changed by telling the ECU that you have different wheels. Would be interesting to know what they actually did...

So would I but they said they only changed to parameter mentioned by Nath and that was it my mpg has jumped from 42 to about 50 hasn't settled yet so it might be going back again yet as it was doing 53 before all this. The confusing thing is I fitted my alloys about 2 months ago and the fault only started last week